<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>css3盒模型.html</title>
    <style>
        .a {
            width: 200px;
            height: 200px;
            background-color: orange;
            border: 10px solid red;
            padding: 30px;
        }
        .b {
            width: 200px;
            height: 200px;
            background-color: skyblue;
            border: 10px solid red;
            box-sizing: border-box;
            padding: 20px;
        }
    </style>
</head>
<body>
    <div class="a">小猪</div>
    <div class="b">大猪</div>
</body>
</html>